The present invention relates to an orthodontic bracket, and in particular such an orthodontic bracket enabling to secure positive pressure effecting to an archwire received in an archwire slot for correcting irregularities of the teeth, and enabling to maintain the pressure for a long time.
FIG. 14A shows an orthodontic bracket 100 correcting a row of teeth. The orthodontic bracket 100 comprises a mask-like base 101 attached to a enamel surface of tooth, a bracket main body 102 furnished on the base 101 at its one side, an archwire slot 103 formed in the bracket main body 102, a guiding part 104 formed at the base side 101 and penetrating in a transverse direction with the archwire slot 103, and a band-like clip 105 guided in the guiding part 104 (hereinafter defined as a prior art example 1).
With respect to the orthodontic bracket 100, the clip 105 is curved in substantial U-shape as covering at least one part of a side (the upper part in FIG. 14A) opposite to the base 101 in the archwire slot 103, holding portions 106, 106 furnished at one end sides in the length direction of the clip 105 are engaged as creeping under cover portions 107, 107 furnished in the bracket main body 102, thereby to press down an archwire (not shown) toward a bottom of the archwire slot 103.
Depending on this orthodontic bracket 100, in comparison with conventional orthodontic brackets, rotational control and torque control of the archwire for correcting irregularities of the teeth or rotated teeth may be improved.
Further, such an orthodontic bracket 100 obtains excellent effects that can solve following problems (i) to (iii) that are occurred when a ligature wire (not shown) is employed.                (i) complication of ligating work;        (ii) complicating treatment of cut-off ends of the ligature wire; and        (iii) reduction of aesthetic appreciation.        
Furthermore, the orthodontic bracket 100 also obtains excellent effects that can solve following problems (i) to (ii) that are occurred when an elastomeric ligature ring is (not shown) is employed.                (i) reduction of ligating force on the archwire owing to its permanent elongation; and        (ii) discoloration by foods and drinks resulting poor aesthetic appreciation.        
Moreover, the orthodontic bracket 100 further obtains excellent effect that can solve hygienic problems by food debris as problems occurring in common when employing the ligature wire or the elastomeric ligature ring. Incidentally, since the above mentioned prior art example 1 makes engagement, as shown in FIG. 14B, by causing the holding portions 106 of the clip 105 to creep under the cover portions 107, if making the rotational control more than a determined amount, the archwire 108 pushes up the clip 105, whereby the holding portion 106 of the clip 105 probably gets out from the cover portion 107 of the bracket main body 102. This problem similarly happens when using a square and rectangular wire near a full size.
On the other hand, the orthodontic bracket 200 shown in FIG. 15A has a groove 210 transverse with the archwire slot 203 of the bracket main body 202 supported by the base 201, and at the same time it has a fitting member 220 made of elastomer or resin having flexibility (U.S. Pat. No. 6,142,775, hereinafter referring a prior art example 2).
This prior art example 2 has bar-like anchoring parts 221, 222 at both ends in the length direction of the fitting member 220, and the anchoring part 222 is engaged with tie-wing parts 209, 209 at an occlusal side of the bracket main body 202, and then if the locking part 221 is engaged with tie-wing parts 208, 208 at a gingival side of the bracket main body, the fitting member presses down the archwire slot.
In addition, the prior art example 2 sets forth that a pair of arms 223, 223 project from a spine of the fitting member 220 as illustrated in FIG. 15B, and if these arms 223, 223 are fitted in the archwire slot 203, the rotational control is made possible.
However, in the prior art example 2, since the fitting member 220 made of elastomer or resin having flexibility presses down into the groove 210 crossing with the archwire slot 203, this embodiment is similar to the case of ligation with the elastomeric ligature ring, and enough effect might be probably little available.
Further, with respect to the prior art example 2, even if the pair of arms 223, 223 projecting from the fitting member 220 are fitted in the archwire slot 203, since each arm 223 has almost equal width and size to those of the archwire slot 203 and is made of elastomer or resin having flexibility, the rotational control might not be effective.
The prior art example 2 is difficult to be handled because of the shape or small size and causes troublesome works to doctors. In addition, the prior art example 2 has a risk of the fitting member 220 getting out from the bracket main body 202 by taking meals or brushing thereafter.
Besides, in the prior art example 2, since the fitting member 220 elastically presses down the archwire 211, a problem occurs that a friction free state is not provided which is required to a fine archwire used at an initial stage.